In recent years, there has been an increasingly strong request for protecting the earth environment. In a refrigerator and other refrigeration cycle equipment, there has been a strong demand particularly for higher efficiency.
A hermetic compressor used for a freezing and refrigerating apparatus, air conditioner, and other refrigeration cycle equipment generally includes an inlet muffler for damping noise generated while a refrigerant gas is being suctioned, in its hermetic enclosure.
One of the causes of reducing the efficiency of a compressor including this inlet muffler is overheating of a refrigerant gas suctioned. The temperature of a refrigerant gas rises due to heat transmitted from some heat sources present inside the compressor until the refrigerant gas permeates the cylinder after it enters the compressor. The temperature rise of the refrigerant gas increases its ratio volume, causing the mass flow rate of the refrigerant gas to decrease.
The cooling performance of a compressor is proportional to the mass flow rate of the refrigerant gas, and thus decrease in the mass flow rate lowers the efficiency. Under the circumstances, patent citation 1 proposes an inlet muffler of a hermetic compressor that minimizes heat transmitted to a low-temperature refrigerant gas suctioned to the cylinder.
Hereinafter, a description is made of a conventional hermetic compressor disclosed in patent citation 1 with reference to the related drawings. FIG. 10 is a longitudinal sectional view of the conventional hermetic compressor described in patent literature 1. FIG. 11 is a sectional view of the substantial part of the conventional hermetic compressor. FIG. 12 is an exploded perspective view of a conventional inlet muffler.
As shown in FIGS. 10 through 12, the conventional hermetic compressor stores lubricating oil 3 at the bottom of hermetic enclosure 1 and is filled with refrigerant gas 20. Compressor unit 5 is elastically supported on hermetic enclosure 1 by suspension spring 7.
Compressor unit 5 is equipped with electromotive element 9, and compressing element 11 disposed above electromotive element 9, where electromotive element 9 includes stator 13 and rotor 15.
Compressing element 11 has crankshaft 17 including eccentric shaft 27 and main shaft 35. Compressing element 11 has block 23 integrally formed with cylinder 21 forming compression chamber 19. Compressing element 11 has piston 25, and valve plate 31 sealing the end surface of cylinder 21. Compressing element 11 has an inlet valve (not shown) for opening and closing inlet hole 33 (refer to FIG. 11) provided in valve plate 31. Compressing element 11 further has joint 29 connecting eccentric shaft 27 to piston 25.
Main shaft 35 of crankshaft 17 is pivotally supported rotatably on bearing 37 of block 23 and has rotor 15 fixed thereto. Crankshaft 17 includes an oiling mechanism (not shown).
Further, inlet muffler 41 is pinched and fixed between valve plate 31 attached onto the end surface of cylinder 21 and cylinder head 39 lidding valve plate 31.
As shown in FIGS. 11, 12, inlet muffler 41 is molded from a synthetic resin such as PBT (polybutylene terephthalate) and PPS (polyphenylene sulfite). Inlet muffler 41 includes muffler body 43 forming a sound absorbing space, and cover 60 having inlet pipe 45 and outlet pipe 47.
Inlet pipe 45 includes inlet-pipe outlet 49 open into muffler body 43. Inlet pipe 45 includes inlet-pipe inlet 51 outside cover 60, open into the space inside hermetic enclosure 1.
Outlet pipe 47 includes outlet-pipe inlet 53 open into muffler body 43. Outlet pipe 47 includes outlet-pipe outlet 55 outside cover 60, connected to cylinder head 39. Here, the arrows in FIG. 11 show the flow of refrigerant gas 20 inside inlet muffler 41.
Hereinafter, a description is made of the operation of a conventional hermetic compressor with the above-described structure. First, the hermetic compressor passes a current through stator 13 to generate a magnetic field, thereby rotating rotor 15 fixed to main shaft 35 to rotate crankshaft 17. This rotation reciprocates piston 25 in and along cylinder 21 through joint 29 rotatably attached onto eccentric shaft 27.
Then, the reciprocating movement of piston 25 makes repeating suction of refrigerant gas 20 into compression chamber 19; compression of gas 20; and discharge of gas 20 into the refrigeration cycle (not shown).
In this case, refrigerant gas 20 suctioned through inlet-pipe inlet 51 passes through inlet pipe 45 and is led into muffler body 43 through inlet-pipe outlet 49. After that, refrigerant gas 20 is suctioned through outlet-pipe inlet 53, passes through outlet pipe 47, and is introduced into compression chamber 19 from outlet-pipe outlet 55 through inlet hole 33.
Here, inlet muffler 41 reduces noise generated by intermittent suction of refrigerant gas 20. In addition, inlet muffler 41 formed from a resin with low heat transmission prevents overheating of refrigerant gas 20 passing through the inside of inlet muffler 41. Further, the space provided between inlet pipe 45 and muffler body 43 prevents heat transmission from high-temperature refrigerant gas 20 remaining in hermetic enclosure 1. These effects eventually increase the mass flow rate of refrigerant gas 20 suctioned into cylinder 21.
Lubricating oil 3 is conveyed from the bottom of hermetic enclosure 1 to compressing element 11 above through the oiling mechanism provided on crankshaft 17 with the aid of a centrifugal force and others caused by rotation of crankshaft 17.
Lubricating oil 3 conveyed first lubricates sliding parts such as those between crankshaft 17 and bearing 37. After that, lubricating oil 3 shatters into hermetic enclosure 1 from the top end of crankshaft 17 to lubricate piston 25, cylinder 21, and others. Additionally, lubricating oil 3 that has shattered adheres to hermetic enclosure 1. When the lubricating oil that has adhered flows down to the bottom through the inner wall surface of hermetic enclosure 1, heat transmits from lubricating oil 3 to hermetic enclosure 1. The heat that has transmitted into hermetic enclosure 1 is dissipated from hermetic enclosure 1 to the outside to cool the hermetic compressor.
Meanwhile, lubricating oil 3 that has shattered in hermetic enclosure 1, together with refrigerant gas 20, is suctioned into muffler body 43 as well. However, when refrigerant gas 20 is led into muffler body 43 at inlet-pipe outlet 49 to decrease the velocity of refrigerant gas 20, lubricating oil 3 is separated from refrigerant gas 20 to remain at the bottom of muffler body 43.
However, in the above-described conventional structure, refrigerant gas 20 led from inlet-pipe outlet 49 into muffler body 43 flows along the inner wall of the bottom of muffler body 43. As a result, lubricating oil 3 suctioned together with refrigerant gas 20, remaining at the bottom of muffler body 43 easily flows into outlet-pipe inlet 53 positioned close to the bottom of muffler body 43. Consequently, a large amount of lubricating oil 3 easily flows into compression chamber 19.
A large amount of lubricating oil 3 flowing into compression chamber 19 increases the load during compression, increases input to the hermetic compressor, and results in insufficient compression of refrigerant gas 20. This causes the freezing capacity to decrease and rapidly fluctuates such as a compression load, thereby undesirably generating noise.
Further, there is a problem of decreasing the performance of the heat exchanger as a result that a large amount of lubricating oil 3 is discharged into the refrigeration cycle.